Flipping the "glutes switch" might sound funny, "but many amateurs play golf with their gluteal muscles shut off," Phillips says. "It comes from a lack of physical activity during the time leading up to the round. And if those muscles aren't firing properly, you're not going to hit the ball the way you're capable of hitting it. You're leaving yardage on the table."

The gluteus maximus (in red) are the largest muscles of the human body.

The muscles of the butt are prime movers in the golf swing. They're greatly responsible for good posture, pelvic rotation, and energy transfer. They take force generated by the legs pushing against the ground and transfer it into more clubhead speed. They also help take stress off the lower portion of the spine as well as the knees, so you can play more golf without increasing risk of injuries. In short, they're the most important muscles in golf. Unfortunately, Phillips says prolonged sitting and/or a lack of exercise can leave yours in atrophy.

"If you're feeling soreness in the lower back, if you're struggling to stay in your posture when you swing, if you're hitting the ball way shorter than guys who are half your size, there's a good chance you need to train these muscles more," says Phillips, who has helped certify more than 15,000 golf-fitness specialists around the world as part of the hugely succesful TPI program.

"Remember, your golf instructors won't be able to do much for you if your body can't move the way it should to swing a golf club properly."

Here, Phillips shows you how to activate the glutes before you play golf or workout, and then how to train them to be stronger and a lot more functional. After just a few weeks of training, you should start to notice you're hitting the ball harder when you play. And if some of those strikes are in the center of the clubface, picking up 20 yards off the tee and getting a club longer with your irons will happen.

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